Conventional virtual machines (VMs) employ virtual disks as its primary form of storage. Virtual disks provide fully encapsulated storage for the virtual machines, thereby simplifying management tasks such as versioning and rollback. They also provide other advantages such as mobility (VMs can be easily moved and/or copied) and isolation (storage domains of multiple VMs are isolated from each other).
Consequently, in a virtual machine system having multiple VMs, each VM has stored in its virtual disk, operating system files and files that are used in providing management services, such as anti-virus scanning, backup, patching, and versioning, to the VM. When a management service is invoked in response to a file operation issued by a VM, the VM executes the program associated with the invoked management service. For example, in response to an “open file” operation, the VM executes an anti-virus scanning program on the file designated to be opened.
The inventors have observed certain inefficiencies with providing management services within the virtual disk framework described above. First, management programs consume both CPU and memory resources allocated to the virtual machines. Second, the installation of management programs (occurring as a result of a software vendor change, for example) and administration of updates to the management programs can be cumbersome because the process has to be repeated for each virtual machine.
Software vendors are providing centralized software to automate the process of administering updates, but at best, this is a partial solution because it does not address the inefficiency associated with resource consumption.
A virtualization aware file system, known as Ventana, extends a conventional distributed file system to virtual machine environments and thus combines the sharing benefits of a distributed file system with versioning, access control, and disconnected operation features that are available with virtual disks. A detailed description of Ventana is provided in a publication from Stanford University, Department of Computer Science, authored by Ben Pfaff, et al. The publication is entitled “Virtualization Aware File Systems: Getting Beyond the Limitations of Virtual Disks.” Although Ventana provides a file system framework that could be used to address some of the issues with conventional delivery of management services, the publication is silent about how this can be done using Ventana.